Difference between nuclear fission and fusion

Fission is the splitting of a large atom into two or more smaller ones.

Fusion is the fusing of two or more lighter atoms into a larger one.

Natural occurrence of the process:

Fission reaction does not normally occur in nature.

Fusion occurs in stars, such as the sun.

Byproducts of the reaction:

Fission produces many highly radioactive particles.

Few radioactive particles are produced by fusion reaction, but if a fission "trigger" is used, radioactive particles will result from that.

Conditions:

Critical mass of the substance and high-speed neutrons are required.

High density, high temperature environment is required.

Energy Requirement:

Takes little energy to split two atoms in a fission reaction.

Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.

Energy Released:

The energy released by fission is a million times greater than that released in chemical reactions; but lower than the energy released by nuclear fusion.

The energy released by fusion is three to four times greater than the energy released by fission.

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(Useful for UPSC General Studies, APPSC Group 1 Group 2 , Mains Material, Paper 1, Paper 4 Section 1 Section 2 Section 3, ROLE AND IMPACT OF SCIENCE AND TECHNOLOGY IN THE DEVELOPMENT OF INDIA, GENERAL AWARENESS WITH THE MODERN TRENDS IN LIFE SCIENCES, DEVELOPMENT & ENVIRONMENT PROBLEMS)